Numerical simulation study on erosion characteristics of desulfurization slurry using shell-and-tube heat exchanger for low-grade waste heat utilization

The wet desulfurization yields slurry with a moderate temperature and stable supply and thus holds promise for waste heat utilization. However, the corrosive nature and solid particle content of desulfurization slurry from the wet desulfurization process pose potential erosion challenges in waste heat utilization heat exchangers, which is an aspect scarcely explored in the existing literature. The present study aimed to investigate the erosion characteristics in desulfurization slurry heat exchangers using numerical simulation approaches, which can offer crucial insights for practical application in low-grade energy recovery. The result identified slurry mass flow rate and composition as essential factors of erosion distribution. Higher mass flow rates enhance heat transfer efficiency. Still, paradoxically, lower flow rates lead to more pronounced erosion, with a slurry mass flow rate of 35 kg/s resulting in nearly double the erosion compared to the benchmark condition of 56 kg/s. This phenomenon is ascribed to lower fluid velocities in the heat tubes, where the influence of changed velocity diminishes, but slurry exhibits more stable flow at higher mass flow rates. Furthermore, it is also observed that both elevated solids content and particle size lead to an increase in erosion rates. The difference in erosion caused by solid particles with particle sizes in the range of 200-350 mu m is marginal. The heat exchanger structure and arrangement also impact fluid flow and erosion. While the difference in fluid flow between vertically and horizontally arranged heat exchangers is negligible, the erosion was significantly reduced to 1/10 in the vertical arrangement. The no-tube-in-window heat exchangers, designed to minimize vibration, exhibit reduced heat transfer capacity alongside diminished and more uniform erosion. The augmentation of tube passes reduces overall erosion but focalizes severe erosion at the slurry inlet, which presents a potential design solution.